1. Field of the Invention
The invention is related to the field of electromagnetic pumps and, in particular, to an inlet check valve for controlling the direction of fluid flow through the pump.
2. Description of the Prior Art
Electromagnetic fluid pumps conventionally have a conical inlet valve member which seats in a mating conical valve seat formed in the inlet housing. Typical use of such conical valve members are in the "reciprocating plunger pump" disclosed by Wertheimer in U.S. Pat. No. 3,400,663 and the "on demand pump" disclosed by Wilkinson in U.S. Pat. No. 4,086,518. Although inlet valves having conical valve members and conical valve seats function well for most applications, this type of valve has poor anti-backflow characteristics and the pump will lose its prime shortly after its operation is terminated. In many applications, however, the pump is located above the fluid source, and the loss of prime after the operation of the pump is terminated is undesirable and having to re-prime the pump is a nuisance. When such pumps are used in a continuous mode, the loss of electrical power for a period long enough for the pump to lose its prime could result in a dangerous condition.
To eliminate this problem, it has been found that flat elastomeric inlet valves have superior anti-backflow characteristics and eliminate the problems encountered with the conical valve members. A typical example of the use of such a flat elastomer inlet valve is in the portable fluid transfer pump disclosed by Hager et al in U.S. Pat. No. 4,101,950. The problem with the flat elastomer inlet valve is that the valve is slightly less efficient than if it had a conical valve. As a result of these varying requirements, the manufacturer is required to make two different pumps to meet the needs of the different applications.
The invention is a solution to this problem which permits the manufacturer to manufacture a single pump structure capable of accepting either a flat elastomeric valve member or a conical valve member.